Strangeness production in antiproton-nucleus collisions

Antiproton annihilations on nuclei provide a very interesting way to study the behaviour of strange particles in the nuclear medium. In low energy $\bar p$ annihilations, the hyperons are produced mostly by strangeness exchange mechanisms. Thus, hyperon production in $\bar p A$ interactions is very sensitive to the properties of the antikaon-nucleon interaction in nuclear medium. Within the Giessen Boltzmann-Uehling-Uhlenbeck transport model (GiBUU), we analyse the experimental data on $\Lambda$ and $K^0_S$ production in $\bar p A$ collisions at $p_{\rm lab}=0.2-4$ GeV/c. A satisfactory overall agreement is reached, except for the $K^0_S$ production in $\bar p+^{20}$Ne collisions at $p_{\rm lab}=608$ MeV/c, where we obtain substantially larger $K^0_S$ production rate. We also study the $\Xi$ hyperon production, important in view of the forthcoming experiments at FAIR and J-PARC.Comment: 8 pages, 4 figures, invited talk given by A.B. Larionov at the 10th International Conference on Low Energy Antiproton Physics (LEAP2011), Vancouver, Canada, Apr 27 - May 1, 2011, Hyperfine Interact. in pres

Novel Orbital Ordering induced by Anisotropic Stress in a Manganite Thin Film

We performed resonant and nonresonant x-ray diffraction studies of a Nd0.5Sr0.5MnO3 thin film that exhibits a clear first-order transition. Lattice parameters vary drastically at the metal-insulator transition at 170K (=T_MI), and superlattice reflections appear below 140K (=T_CO). The electronic structure between T_MI and T_CO is identified as A-type antiferromagnetic with the d_{x2-y2} ferroorbital ordering. Below T_CO, a new type of antiferroorbital ordering emerges. The accommodation of the large lattice distortion at the first-order phase transition and the appearance of the novel orbital ordering are brought about by the anisotropy in the substrate, a new parameter for the phase control.Comment: 4pages, 4figure

Volatilization of alkali metals from the heated Murchison (CM2) meteorite

In order to examine volatilization processes of alkali metals at high temperature, heating experiments were carried out using a starting material prepared from Murchison (CM2) (grain-size : ∿10μm) at temperatures of 1200-1400℃ under a constant pressure of 8×10^ Torr, and heating duration up to 80min. Analyses of alkalis (Na, K, Rb), major and minor elements and petrographic examinations were performed for run products. Results show that fractional volatilization of alkali metals occurred during heating. It is suggested that the volatilization rates of alkali metals are influenced by the chemical composition of partial melt

Near-Optimal Scheduling for LTL with Future Discounting

We study the search problem for optimal schedulers for the linear temporal logic (LTL) with future discounting. The logic, introduced by Almagor, Boker and Kupferman, is a quantitative variant of LTL in which an event in the far future has only discounted contribution to a truth value (that is a real number in the unit interval [0, 1]). The precise problem we study---it naturally arises e.g. in search for a scheduler that recovers from an internal error state as soon as possible---is the following: given a Kripke frame, a formula and a number in [0, 1] called a margin, find a path of the Kripke frame that is optimal with respect to the formula up to the prescribed margin (a truly optimal path may not exist). We present an algorithm for the problem; it works even in the extended setting with propositional quality operators, a setting where (threshold) model-checking is known to be undecidable

Field-induced metal-insulator transition and switching phenomenon in correlated insulators

We study the nonequilibrium switching phenomenon associated with the metal-insulator transition under electric field E in correlated insulator by a gauge-covariant Keldysh formalism. Due to the feedback effect of the resistive current I, this occurs as a first-order transition with a hysteresis of I-V characteristics having a lower threshold electric field (\sim 10^4 Vcm^{-1}) much weaker than that for the Zener breakdown. It is also found that the localized mid-gap states introduced by impurities and defects act as hot spots across which the resonant tunneling occurs selectively, which leads to the conductive filamentary paths and reduces the energy cost of the switching function.Comment: 5 pages, 3 figures. A study on the metal-insulator transition in correlated insulators was adde

Ultrafast Photoinduced Formation of Metallic State in a Perovskite-type Manganite with Short Range Charge and Orbital Order

Femtosecond reflection spectroscopy was performed on a perovskite-type manganite, Gd0.55Sr0.45MnO3, with the short-range charge and orbital order (CO/OO). Immediately after the photoirradiation, a large increase of the reflectivity was detected in the mid-infrared region. The optical conductivity spectrum under photoirradiation obtained from the Kramers-Kronig analyses of the reflectivity changes demonstrates a formation of a metallic state. This suggests that ferromagnetic spin arrangements occur within the time resolution (ca. 200 fs) through the double exchange interaction, resulting in an ultrafast CO/OO to FM switching.Comment: 4 figure

Exploiting the Temporal Logic Hierarchy and the Non-Confluence Property for Efficient LTL Synthesis

The classic approaches to synthesize a reactive system from a linear temporal logic (LTL) specification first translate the given LTL formula to an equivalent omega-automaton and then compute a winning strategy for the corresponding omega-regular game. To this end, the obtained omega-automata have to be (pseudo)-determinized where typically a variant of Safra's determinization procedure is used. In this paper, we show that this determinization step can be significantly improved for tool implementations by replacing Safra's determinization by simpler determinization procedures. In particular, we exploit (1) the temporal logic hierarchy that corresponds to the well-known automata hierarchy consisting of safety, liveness, Buechi, and co-Buechi automata as well as their boolean closures, (2) the non-confluence property of omega-automata that result from certain translations of LTL formulas, and (3) symbolic implementations of determinization procedures for the Rabin-Scott and the Miyano-Hayashi breakpoint construction. In particular, we present convincing experimental results that demonstrate the practical applicability of our new synthesis procedure

Layer dynamics of a freely standing smectic-A film

We study the hydrodynamics of a freely-standing smectic-A film in the isothermal, incompressible limit theoretically by analyzing the linearized hydrodynamic equations of motion with proper boundary conditions. The dynamic properties for the system can be obtained from the response functions for the free surfaces. Permeation is included and its importance near the free surfaces is discussed. The hydrodynamic mode structure for the dynamics of the system is compared with that of bulk systems. We show that to describe the dynamic correlation functions for the system, in general, it is necessary to consider the smectic layer displacement $u$ and the velocity normal to the layers, $v_z$, together. Finally, our analysis also provides a basis for the theoretical study of the off-equilibrium dynamics of freely-standing smectic-A films.Comment: 22 pages, 4 figure